This section provides background information related to the present disclosure which is not necessarily prior art.
The present invention generally relates to therapy and physical fitness equipment, and more particularly to devices capable of stretching the calf muscle-Achilles tendon unit.
The Achilles tendon connects the calf muscles to the heel of the foot. The calf muscles pull on the heel through the Achilles tendon, enabling propulsion of the human body through the foot for walking and jumping activities. The combined length of the calf muscles and Achilles tendon should be short enough to contract strongly and generate enough power for daily activities, and also permit sufficient stretching to allow about ten to twenty degrees of ankle dorsiflexion. If the calf muscles and Achilles tendon cannot stretch and allow ankle dorsiflexion to this extent, the midfoot and the forefoot see abnormal stresses leading to pain and conditions like plantar fasciitis, flat feet, posterior tibial tendon dysfunction, stress fracture, and arthritis.
The normal human foot is a dynamic structure that can function as a flexible unit capable of adapting to uneven support surfaces during weight bearing, as well as a rigid unit capable of forward propulsion through tightening of the calf muscles. The loosening and stiffening of the foot automatically occur as a result of locking and unlocking the midfoot during walking and running. The same mechanism can be used in a reverse fashion to lock the midfoot and stiffen the foot by maximally lifting the big toe (hallux) and its metatarsal bone away from the ground or the level of the fifth toe and its metatarsal bone (supination of the forefoot). One can also pronate the forefoot by elevating the fifth metatarsal relative to the first metatarsal, which results in unlocking the foot and stretching the arch of the foot.
The Achilles tendon can be stretched by daily activities and specific exercises that force the forefoot (toes and metatarsus) toward the leg. In adults, weight-bearing exercises are generally more useful for stretching the Achilles tendon, whereas in children stretching is typically best accomplished with the assistance of an adult. Dynamic splints that provide constant stretching of the tendon can be used by both adults and children. However, such devices achieve limited stretching of the Achilles tendon because stretching of the calf muscle-Achilles tendon unit is more effective if the foot acts as a rigid lever and transmits all the stretch to the Achilles. If the foot is not rigid, some of the stretching forces tend to stretch the arch of the foot and can create or worsen an existing flatfoot condition.